Camera traps offer reliable estimates compared to ground surveys for monitoring duck pairs and broods

Abstract

Monitoring breeding waterfowl populations with ground-based pair and brood surveys informs management and conservation decisions. However, surveys are often limited temporally and may miss individuals that are not present or available for detection at the time of the survey. Alternative methods to monitor waterfowl such as camera traps may be more appropriate to measure relative abundance, but it is unknown how camera trap surveys compare to ground-based surveys. We conducted concurrent walk-up pair and brood surveys on 20 wetlands in Manitoba, Canada and deployed cameras set to take pictures at 10-min intervals during daylight hours. We compared indices of relative abundance and species richness of ducks and ducklings on small prairie wetlands (<3.8 ha) detected with ground-based and camera trap surveys and make recommendations regarding the time of day and duration of camera surveys. As predicted, camera surveys detected more ducks, ducklings, and duck species than ground surveys counted. Importantly, camera surveys detected ducks and ducklings at wetlands that ground surveys did not. Both duck and duckling observations were positively associated between survey methods (ducks: R2 = 0.22, F1,17 = 4.83, P = 0.04, ducklings: R2 = 0.49, F1,15 = 14.16, P = 0.002). We found that cameras are a useful tool to survey relative duck abundance, and the extended temporal surveillance of cameras reduces false negatives.